This invention relates to three-wheeled vehicles, principally human-powered three-wheeled vehicles, although the teachings of the invention also have application to three-wheeled vehicles powered by internal combustion engines or the equivalent.
Various three-wheeled human-powered vehicles have been known for many years. The common child""s tricycle exemplifies such known vehicles. In a conventional tricycle, the child sits on a seat fixed with respect to the vehicle frame. Freewheeling rear wheels are carried by the frame, and steering is accomplished by turning a front wheel pivoted to the frame at a steering head; the child propels the vehicle by way of pedals connected directly to the front wheel. The more recent xe2x80x9cBig Wheelxe2x80x9d is conceptually identical, although having a different appearance due to the rider""s relatively recumbent seating position, and because the Big Wheel is assembled largely of molded plastic components, rather than having a fabricated painted steel frame as does a conventional tricycle.
In U.S. Pat. No. 3,504,934, Wallis teaches a three-wheeled vehicle which can be human- or engine-powered. As in a conventional tricycle, the rider sits on a seat fixed to a frame, and a front wheel is pivotally attached to this frame for steering. However, in Wallis, the rear wheels are carried by a rear subframe, which is attached to the main frame by one of several types of pivoted joint allowing the main frame to lean into a turn, as in a conventional bicycle, and allowing the rear wheels to follow the direction of travel of the vehicle. The angle of the pivot axis defined between the main frame and subframe with respect to the horizontal is not specified, but appears to be relatively close, perhaps within 25xc2x0, to the horizontal.
Mulcahy U.S. Pat. No. 4,359,231 shows a three-wheeled vehicle having a front subframe carrying a front wheel, the axis of which is fixed with respect to the front subframe, and a rear subframe carrying a pair of rear wheels, the axis of which is similarly fixed with respect to the rear subframe. The rider sits on the front subframe, but his or her back is received by a back rest fixed to the rear subframe. The front and rear subframes are pivoted to one another at a pivot point inclined with respect to the vertical, so that as the rider leans to one side, the rear subframe is pivoted with respect to the front subframe, whereby the rear wheels steer the vehicle and the front wheel leans into the turn, as in a conventional bicycle.
As noted, in the Mulcahy vehicle, the rider""s posterior is received by a seat secured to the front subframe, while his or her back is received by a back rest secured to the rear subframe; this would appear to be extremely uncomfortable. The Mulcahy vehicle as shown places the pivot axis at which the front and rear subframes pivot with respect to one another just forward of the rear axle; according to the experiments of the present inventors, as discussed further below, such a vehicle would be violently unstable and extremely difficult to ride with any degree of confidence.
Other two- and three-wheeled vehicles of varying design are shown by the following patents: U.S. Pat. No. 3,620,547 to Vavarek, U.S. Pat. No. 3,669,468 to Rich, U.S. Pat. No. 3,282,606 to Casner, U.S. Pat. No. 3,442,528 to Rademacher, U.S. Pat. No. 3,311,388 to Ryan et al, U.S. Pat. No. 3,981,516 to Haggkvist, U.S. Pat. No. 4,103,921 to Brooks et al, U.S. Pat. No. 3,392,991, also to Ryan et al, U.S. Pat. No. 4,198,072 to Hopkins, U.S. Pat. No. 5,568,935 to Mason, U.S. Pat. No. 4,526,392 to Berkstresser, U.S. Pat. No. 4,279,429 to Hopkins et al, U.S. Pat. No. 4,432,561 to Feikema et al, U.S. Pat. No. 1,494,364 to McGrath, U.S. Pat. No. 2,812,194 to Ajero, U.S. Pat. No. 4,826,190 to Hartmann, and U.S. Pat. No. 4,109,927 to Harper, and by design Pat. No. 280,309 to Forbes et al.
The invention concerns a novel three-wheeled vehicle having a forward portion including a front wheel, and on which the rider sits, and a rear portion having spaced rear wheels. The front portion is pivoted to the rear portion at an inclined steering pivot joint located behind the rider""s seat, so that the vehicle is steered by the rider leaning in the desired direction. The handling characteristics of the vehicle are controlled by the selection of several critical dimensions of various components.